Menstrual Cycle

What is the menstrual cycle?

The menstrual cycle is our fifth vital sign and a fundamental indicator of reproductive health. It comprises a series of physical and hormonal changes in the body that repeat monthly and prepare your body for a possible pregnancy.

Knowing about this exciting process is crucial to boosting your reproductive health, enabling family planning and improving your overall health care.

In this article, we will provide you with an in-depth insight into the menstrual cycle as a fascinating phenomenon of the female body. We want to help you understand and appreciate this complex but vital biological process of your body.

What are the different phases of the menstrual cycle?

The menstrual cycle has two main phases: the follicular phase and the luteal phase.

The follicular phase begins with menstruation and ends with ovulation. The luteal phase begins after ovulation and ends with the next menstruation.

To make the cycle even easier to visualize, it is often divided into four main phases: Menstrual phase, Follicular phase, Ovulatory phase and Luteal phase. During the cycle, the female body goes through these phases at regular intervals.

Each of these phases is characterized by specific hormonal changes and physical adjustments that can affect you both physically and emotionally.



The menstrual phase marks day 1, i.e. the start of your cycle. If no fertilization has taken place in your previous cycle, the body breaks down the lining of the uterus. This leads to menstrual bleeding, also known as a period.

This phase usually lasts between 3 and 7 days, and for many women is accompanied by menstrual pain, cramps and other premenstrual symptoms.

How long does my period normally last?

Your period typically lasts between three and seven days. However, this time frame can vary from cycle to cycle and depends on various factors such as age, hormonal fluctuations, diet, stress and physical activity.

How much blood do you lose on average during menstruation?

The average amount of Period Blood is around 35ml, which is roughly equivalent to the contents of a small espresso cup.

However, quantities between 10 and 80 ml are generally considered normal. Some menstruating women experience particularly heavy bleeding or other cycle disorders.

Follicular phase

The follicular phase begins after menstruation. The duration of the follicular phase can vary from person to person, but is typically between 10 and 14 days.

During the follicular phase, the brain, or more precisely the pituitary gland, stimulates the release of follicle-stimulating hormone (FSH). This hormone promotes the growth and maturation of the follicles in the ovaries. Follicles are cavities that each contain an egg cell.

The hormone oestrogen is produced in the walls of these follicles. As the follicles mature, the oestrogen level rises steadily. As a result, the lining of the uterus is rebuilt, better supplied with blood and more nutrients.

During this process, one of the follicles becomes dominant and matures to its largest size.

The follicular phase ends with the onset of ovulation and the transition to the next phase of the menstrual cycle, the ovulation phase.

Ovulation phase, ovulation and the fertile window

The ovulation phase is the shortest phase of the menstrual cycle.

It only lasts around sixteen to 32 hours and begins with a rise in luteinizing hormone (LH). The luteinizing hormone is released in response to the signal from the pituitary gland in response to the previously increased oestrogen level.

The luteinizing hormone triggers ovulation by causing the dominant follicle (egg follicle) to burst and release the egg into the ovary.

It should be noted that there can be more than one surge in luteinizing hormone before ovulation is triggered.

When do you ovulate?

Your ovulation usually occurs around the middle of your menstrual cycle, i.e. around day 14 in an average cycle of 28 days. However, the exact time of ovulation varies from woman to woman and even from cycle to cycle.

More specifically, you ovulate around 10 to 12 hours after the LH hormone surge. This time marks the peak of your fertility in the cycle.

How can you recognize your ovulation?

There are various methods to recognize your ovulation. Some women feel physical signs such as mittelschmerz, a slight twinge in the lower abdomen, which can indicate ovulation. In addition, cervical mucus or ovulation tests can also provide information about ovulation.

A particularly popular method is basal body temperature monitoring. Basal body temperature changes over the course of your cycle and rises shortly after ovulation.

Cycle computers such as Daysy offer you modern and convenient solutions for tracking your basal body temperature. Daysy shows you directly on the device with a red flashing light when your predicted ovulation occurs. You can also follow the development of your temperature curve in detail in the DaysyDay app. So you can always keep an eye on your ovulation.


When are your fertile days?

Fertile days refer to the period in a woman's menstrual cycle when she is most likely to conceive and can best plan to get pregnant.

Although the most fertile time is marked by the time of ovulation, sexual intercourse can also lead to pregnancy a few days before you ovulate.

The reason for this is that sperm can survive in a woman's body for up to 5 days.

Your fertile window therefore begins five days before ovulation and ends the day after you ovulate. This results in a period of 6 days during which you are fertile.

Knowing about the fertile window and ovulation is crucial for couples planning a pregnancy. This allows you to identify the most fertile days during your menstrual cycle and significantly increase your chances of successful conception.

Daysy offers an ideal solution for determining your fertile days. Daysy automatically signals your fertile days with a red light on the device.

Luteal phase

The luteal phase, also known as the corpus luteum phase, begins directly after ovulation and lasts until the start of the next menstruation. This period lasts approximately 14 days, but can vary between 10 and 16 days.

Compared to the follicular phase, the duration of the luteal phase remains fairly constant. A healthy luteal phase lasts at least 9 days.

After ovulation, a temporary gland, also known as the corpus luteum, develops in the ovary from the empty follicle. This produces the hormone progesterone, which maintains the lining of the uterus for a possible pregnancy and prepares for implantation of the fertilized egg.

During this time, the egg travels through the fallopian tube to the uterus for around 5 days.

What happens in the luteal phase if fertilization has taken place?

If the egg is fertilized, it nests in the lining of the uterus about a week after fertilization, the corpus luteum remains intact and continues to produce progesterone.

Daysy shows can indicate a potential pregnancy. You can recognize the prediction either in the DaysyDay app or directly on the device. Daysy recognizes a potential pregnancy based on a constantly elevated basal body temperature that remains at a consistently high level of around 37° Celsius for more than 18 days.

What happens in the luteal phase if fertilization has not taken place?

If fertilization does not take place, the hormone level of progesterone drops again and the unfertilized egg is rejected.

This leads to the uterine lining shedding and being excreted together with the egg during the subsequent period.

This marks the start of your new menstrual cycle and the cyclical miracle begins all over again.

What significance does the menstrual cycle have for women's health?

The importance of your menstrual cycle is not limited to fertility and well-being, but also serves as an important indicator of your general state of health.

As the fifth vital sign, it provides important information about your health, similar to breathing or pulse. A regular and healthy cycle indicates normal hormonal regulation and production in your body.

If you notice any abnormalities, this can indicate possible hormonal imbalances or illnesses, such as. polycystic ovary syndrome (PCOS) or endometriosis.

These irregularities are initially no reason to panic, but recognizing them can help you to seek medical help at an early stage. Understanding your own cycle can therefore be crucial for the early detection and treatment of such conditions.


How long does the cycle last on average?

The average cycle length is around 21-35 days, but can vary from woman to woman. You don't need to worry about fluctuations of up to 7 days, but larger deviations should be clarified by a doctor.

To calculate the length of your cycle, note the period from the first day of your period to the day before the start of your next period. This understanding of your individual cycle length provides you with valuable insights into your body.

How can you easily track the duration and different phases of your menstrual cycle?

You can track your cycle particularly easily using your basal body temperature. It is measured directly after waking up with a special basal thermometer or cycle computer, such as Daysy.

Within a cycle, the temperature fluctuations triggered by the hormones range from 0.2° to 0.45° degrees Celsius. You can then track these subtle changes with the DaysyDay app using the temperature curve.

Thanks to Daysy, you don't have to write anything down. You automatically receive practical information such as the duration of your cycle and the time of ovulation. This gives you exciting insights into your body and you always know exactly which phase of your menstrual cycle you are in.

What types of menstrual irregularities are there?

In addition to the cycle disorders mentioned above, specific menstrual disorders can also occur that can significantly affect your quality of life.

What happens if your period is absent or too infrequent?

If you miss your period even though you are not pregnant, breastfeeding or in the menopause, this is called amenorrhea.

An infrequent period, where the interval between periods is consistently more than 35 days, is called oligomenorrhea.

Cycle disorders can be caused by various factors such as hormonal imbalances, extreme weight loss or weight gain, stress and chronic illnesses.

What if your menstrual bleeding is very heavy?

Excessively heavy or prolonged menstrual bleeding, also known as menorrhagia, can have a major impact on your everyday life and is often a sign of existing illnesses.

If you keep an eye on your cycle, you can discuss any of these abnormalities in your cycle or menstrual bleeding directly with your doctor.

What additional physical and psychological influences does the menstrual cycle have on the female body?

The menstrual cycle affects your body in various ways, both physically and psychologically. These influences can be triggered by hormonal changes during your cycle. You may experience the following effects during your cycle:

In addition, many women experience a variety of symptoms on the days before their period, such as pain, breast tenderness, mood swings or even headaches. These symptoms are known as premenstrual syndrome and can have a major impact on women's everyday lives. The same applies here: if you notice severe PMS symptoms, it is advisable to seek medical advice.

So you can see how different the influences on your body can be. However, all the effects that occur are as different as we women ourselves. That's why it can be incredibly interesting to be able to assign these effects to your personal cycle phases.

What factors influence the menstrual cycle?

Just as diverse as the effects of the menstrual cycle on your body are the factors that can influence your cycle. They can range from small changes to your routine to external influences.

For example, your sleep-wake cycle, travel, shift work or stress can influence your body's physiological processes. Your body fat percentage also has a direct influence on your cycle.

Thanks to modern cycle computers, you can still track your cycle in all phases of your life. Daysy automatically adapts to your individual circumstances and reliably shows you your fertile and non-fertile days.


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